X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=urcu-defer.c;h=a38b5c0b9418af76287b3e552fd089f278cb5e55;hp=13f94fa0f05b05833152265da9147bdb456e88b6;hb=64c4cafd597aff7423be003dcf41735904126f66;hpb=04eb9c4f11a43e4cd7307d319b2d5f7624cd2801 diff --git a/urcu-defer.c b/urcu-defer.c index 13f94fa..a38b5c0 100644 --- a/urcu-defer.c +++ b/urcu-defer.c @@ -28,7 +28,6 @@ #include #include #include -#include #include #include #include @@ -38,6 +37,8 @@ #include "urcu-defer.h" #define futex(...) syscall(__NR_futex, __VA_ARGS__) +#define FUTEX_WAIT 0 +#define FUTEX_WAKE 1 void __attribute__((destructor)) urcu_defer_exit(void); @@ -56,19 +57,7 @@ static int defer_thread_futex; * the reclamation tread. */ static struct defer_queue __thread defer_queue; - -/* Thread IDs of registered deferers */ -#define INIT_NUM_THREADS 4 - -struct deferer_registry { - pthread_t tid; - struct defer_queue *defer_queue; - unsigned long last_head; -}; - -static struct deferer_registry *registry; -static int num_deferers, alloc_deferers; - +static LIST_HEAD(registry); static pthread_t tid_defer; static void internal_urcu_lock(pthread_mutex_t *mutex) @@ -110,9 +99,9 @@ static void internal_urcu_unlock(pthread_mutex_t *mutex) */ static void wake_up_defer(void) { - if (unlikely(atomic_read(&defer_thread_futex) == -1)) { - atomic_set(&defer_thread_futex, 0); - futex(&defer_thread_futex, FUTEX_WAKE, 0, + if (unlikely(uatomic_read(&defer_thread_futex) == -1)) { + uatomic_set(&defer_thread_futex, 0); + futex(&defer_thread_futex, FUTEX_WAKE, 1, NULL, NULL, 0); } } @@ -120,12 +109,12 @@ static void wake_up_defer(void) static unsigned long rcu_defer_num_callbacks(void) { unsigned long num_items = 0, head; - struct deferer_registry *index; + struct defer_queue *index; internal_urcu_lock(&urcu_defer_mutex); - for (index = registry; index < registry + num_deferers; index++) { - head = LOAD_SHARED(index->defer_queue->head); - num_items += head - index->defer_queue->tail; + list_for_each_entry(index, ®istry, list) { + head = LOAD_SHARED(index->head); + num_items += head - index->tail; } internal_urcu_unlock(&urcu_defer_mutex); return num_items; @@ -136,15 +125,15 @@ static unsigned long rcu_defer_num_callbacks(void) */ static void wait_defer(void) { - atomic_dec(&defer_thread_futex); + uatomic_dec(&defer_thread_futex); smp_mb(); /* Write futex before read queue */ if (rcu_defer_num_callbacks()) { smp_mb(); /* Read queue before write futex */ /* Callbacks are queued, don't wait. */ - atomic_set(&defer_thread_futex, 0); + uatomic_set(&defer_thread_futex, 0); } else { smp_rmb(); /* Read queue before read futex */ - if (atomic_read(&defer_thread_futex) == -1) + if (uatomic_read(&defer_thread_futex) == -1) futex(&defer_thread_futex, FUTEX_WAIT, -1, NULL, NULL, 0); } @@ -196,7 +185,6 @@ static void _rcu_defer_barrier_thread(void) rcu_defer_barrier_queue(&defer_queue, head); } - void rcu_defer_barrier_thread(void) { internal_urcu_lock(&urcu_defer_mutex); @@ -219,16 +207,16 @@ void rcu_defer_barrier_thread(void) void rcu_defer_barrier(void) { - struct deferer_registry *index; + struct defer_queue *index; unsigned long num_items = 0; - if (!registry) + if (list_empty(®istry)) return; internal_urcu_lock(&urcu_defer_mutex); - for (index = registry; index < registry + num_deferers; index++) { - index->last_head = LOAD_SHARED(index->defer_queue->head); - num_items += index->last_head - index->defer_queue->tail; + list_for_each_entry(index, ®istry, list) { + index->last_head = LOAD_SHARED(index->head); + num_items += index->last_head - index->tail; } if (likely(!num_items)) { /* @@ -238,9 +226,8 @@ void rcu_defer_barrier(void) goto end; } synchronize_rcu(); - for (index = registry; index < registry + num_deferers; index++) - rcu_defer_barrier_queue(index->defer_queue, - index->last_head); + list_for_each_entry(index, ®istry, list) + rcu_defer_barrier_queue(index, index->last_head); end: internal_urcu_unlock(&urcu_defer_mutex); } @@ -336,62 +323,11 @@ void rcu_defer_queue(void (*fct)(void *p), void *p) _rcu_defer_queue(fct, p); } -static void rcu_add_deferer(pthread_t id) -{ - struct deferer_registry *oldarray; - - if (!registry) { - alloc_deferers = INIT_NUM_THREADS; - num_deferers = 0; - registry = - malloc(sizeof(struct deferer_registry) * alloc_deferers); - } - if (alloc_deferers < num_deferers + 1) { - oldarray = registry; - registry = malloc(sizeof(struct deferer_registry) - * (alloc_deferers << 1)); - memcpy(registry, oldarray, - sizeof(struct deferer_registry) * alloc_deferers); - alloc_deferers <<= 1; - free(oldarray); - } - registry[num_deferers].tid = id; - /* reference to the TLS of _this_ deferer thread. */ - registry[num_deferers].defer_queue = &defer_queue; - registry[num_deferers].last_head = 0; - num_deferers++; -} - -/* - * Never shrink (implementation limitation). - * This is O(nb threads). Eventually use a hash table. - */ -static void rcu_remove_deferer(pthread_t id) -{ - struct deferer_registry *index; - - assert(registry != NULL); - for (index = registry; index < registry + num_deferers; index++) { - if (pthread_equal(index->tid, id)) { - memcpy(index, ®istry[num_deferers - 1], - sizeof(struct deferer_registry)); - registry[num_deferers - 1].tid = 0; - registry[num_deferers - 1].defer_queue = NULL; - registry[num_deferers - 1].last_head = 0; - num_deferers--; - return; - } - } - /* Hrm not found, forgot to register ? */ - assert(0); -} - static void start_defer_thread(void) { int ret; - ret = pthread_create(&tid_defer, NULL, thr_defer, - NULL); + ret = pthread_create(&tid_defer, NULL, thr_defer, NULL); assert(!ret); } @@ -408,39 +344,42 @@ static void stop_defer_thread(void) void rcu_defer_register_thread(void) { - int deferers; + int was_empty; + + assert(defer_queue.last_head == 0); + assert(defer_queue.q == NULL); + defer_queue.q = malloc(sizeof(void *) * DEFER_QUEUE_SIZE); internal_urcu_lock(&defer_thread_mutex); internal_urcu_lock(&urcu_defer_mutex); - defer_queue.q = malloc(sizeof(void *) * DEFER_QUEUE_SIZE); - rcu_add_deferer(pthread_self()); - deferers = num_deferers; + was_empty = list_empty(®istry); + list_add(&defer_queue.list, ®istry); internal_urcu_unlock(&urcu_defer_mutex); - if (deferers == 1) + if (was_empty) start_defer_thread(); internal_urcu_unlock(&defer_thread_mutex); } void rcu_defer_unregister_thread(void) { - int deferers; + int is_empty; internal_urcu_lock(&defer_thread_mutex); internal_urcu_lock(&urcu_defer_mutex); - rcu_remove_deferer(pthread_self()); + list_del(&defer_queue.list); _rcu_defer_barrier_thread(); free(defer_queue.q); defer_queue.q = NULL; - deferers = num_deferers; + is_empty = list_empty(®istry); internal_urcu_unlock(&urcu_defer_mutex); - if (deferers == 0) + if (is_empty) stop_defer_thread(); internal_urcu_unlock(&defer_thread_mutex); } void urcu_defer_exit(void) { - free(registry); + assert(list_empty(®istry)); }